Semiconductor strain gauge and the manufacturing method

ABSTRACT

A high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate around the diffuse resistance region is provided, one side of the electrodes is formed extending to the high-density impurity diffused layer and the diffused resistance region and the high-density impurity diffused layer are connected in a semiconductor strain gauge that is formed on the surface of the semiconductor substrate of a fixed conduction type and is provided with the diffused resistance region of opposite conduction type to the semiconductor substrate and is provided with electrodes on both ends of the diffused resistance region.

BACKGROUND OF THE INVENTION

This invention relates to the structure and manufacturing method of a semiconductor gauge using the diffused resistor, and it can be used for various acceleration sensor pressure sensor, etc.

A strain gauge is used to detect acceleration and pressure in the prior art and there are various types in the strain gauge. The strain gauge using a semiconductor single crystal is used in many cases, which detects the changes in force applied utilizing the piezoelectric resistance effect of the semiconductor as variation in electric resistance. There are a bulk type gauge and a diffused type gauge in the semiconductor strain gauge using the piezoelectric resistance effect and it is necessary to apply manufacturing work on the semiconductor substrate because the semiconductor substrate itself becomes a gauge in each type.

FIG. 7 shows the structure of a diffused type gauge to be used commonly since the past and (a) is a vertical sectional view and (b) is a plane view viewed from an arrow A-A line direction in (a). The diffused resistor 2 of opposite conduction type is formed, diff-using a type P impurity on the surface of type N single crystal silicone substrate 1. The surface of the diffused resistor 2 is protected with oxide film 3 such as SiO₂, which is an insulated film and a positive (+) electrode 4 and a negative (−) electrode 5 are formed by metallic film of aluminum and the like by etching a part of the oxide film 3. It is not necessary to process the semiconductor substrate mechanically when the resistance layer is formed on the type N single crystal silicone substrate 1 as the semiconductor substrate by diffusion.

-   -   [Patent document 1] U.S. Pat. No. 6,635,910     -   [Patent document 2] JP, 2001-264188, Publication of unexamined         patent applications     -   [Patent document 3] JP, 2004-531699, PCT Publication of         unexamined patent applications

SUMMARY OF THE INVENTION

However, the structure of a diffused type gauge in the prior art is that the type P resistor 2 is only formed on the surface of type N semiconductor substrate, that is to say, type N single crystal silicone substrate 1 by the diffusion and therefore, it is under the condition in which a channel can be generated easily under the oxide film (insulated film) 3 by the impurity in the circumference or charge and then the impurity density of the type N semiconductor substrate is low. Therefore, the route where electric current flows may exists in the region other than the part of the type P diffused resistor 2 and it has become a problem that the resistance of the diffused type gauge becomes unstable.

The semiconductor strain gauge and the manufacturing method relating to this invention are to prevent generation of channel in the diffused type strain gauge. When impurity and charge are stuck around the type P diffused resistor 2, or when the impurity density of the semiconductor substrate, that is, of the type N single crystal silicone substrate 1 is low, the generation of channel which is easy to be generated between electrodes pads is prevented and the output of the diffused type gauge is stabilized, for example, the above described problem is solved by opposite conduction type of impurity diffused layer of high-density around the type P diffused resistor. That is to say, this invention is characterized by that in which a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate around the diffused resistance region is provided, in which one side of the electrodes is formed extending to the high-density impurity diffused layer and the diffused resistance region and the high-density impurity diffused layer are connected, and in which the voltage in which the leak from the diffused resistance region to the high-density impurity diffused layer is not generated is applied to the electrode, in a semiconductor strain gauge which is provided with a semiconductor substrate of a fixed conduction type, diffused resistance region of opposite conduction type to the semiconductor substrate formed on the surface of the semiconductor substrate and electrodes prepared on both end parts of the diffused resistance region.

And, this invention is characterized by that in which a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate around the diffused resistance region is provided, in which any one of the electrodes is formed extending to the high-density impurity diffused layer and the diffused resistance region and the high-density impurity diffused layer are connected, and in which the voltage in which the leak from the diffused resistance region to the high-density impurity diffused layer is not generated is applied to the electrode, in a semiconductor strain gauge which is provided with a semiconductor substrate of a fixed conduction type, diffused resistance region of opposite conduction type to the semiconductor substrate formed on the surface of the semiconductor substrate and electrodes prepared on both end parts and a middle part of the diffused resistance region so that it can be a half bridge structure.

And, this invention is characterized by that in which a high density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate around the diffused resistance region is provided, in which any one of the electrodes is formed extending to the high-density impurity diffused layer and the diffused resistance region and the high-density impurity diffused layer are connected, and in which the voltage in which the leak from the diffused resistance region to the high-density impurity diffused layer is not generated is applied to the electrode, in a semiconductor strain gauge which is provided with a semiconductor substrate of a fixed conduction type, diffused resistance region of opposite conduction type to the semiconductor substrate formed on the surface of the semiconductor substrate and electrodes prepared at four places of the diffused resistance region so that it can be a full bridge structure.

And, this invention is characterized by that in which a high-density impurity diffused layer of the opposite conduction type to the semiconductor substrate is formed in a part of the diffused resistance region and also is connected to the electrode.

And, this invention is characterized by that in which the interval between the diffused resistance region and the high-density impurity diffused layer is 5 μm or more.

And, this invention is characterized by that in which the diffused resistance region of the opposite conduction type to the semiconductor substrate is formed on the surface of a fixed conduction type, a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate is formed around the diffused resistance region, a guard film is formed on the surface of the semiconductor substrate, parts of the guard film in a part of two places of the diffused resistance region and on upper plane of a part of the high-density impurity diffused layer are removed, and two electrode films of which one film is connected to one place of the diffused resistance region and the other film is connected to the high density impurity diffused layer and the other places of the diffused resistance region are formed.

This invention is characterized by that in which the diffused resistance region of the opposite conduction type to the semiconductor substrate, consisting of a half bridge structure is formed on the surface of a fixed conduction type, a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate is formed around the diffused resistance region, a guard film is formed on the surface of the semiconductor substrate, parts of the guard film in a part of three places of the diffused resistance region and on upper plane of a part of the high-density impurity diffused layer are removed, and three electrode films of which any one film is connected to the high-density impurity diffused layer are formed.

In addition, this invention is characterized by that in which the diffused resistance region of the opposite conduction type to the semiconductor substrate, consisting of a full bridge structure is formed on the surface of a fixed conduction type, a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate is formed around the diffused resistance region, a guard film is formed on the surface of the semiconductor substrate, parts of the guard film in a part of four places of the diffused resistance region and on upper plane of a part of two places of the high-density impurity diffused layer are removed, and four electrode films of which any one film is connected to the high density impurity diffused layer are formed.

The semiconductor strain gauge relating to this invention and the manufacturing method have the following effects and they have above described structure and function. The invention described in claim 1 through claim 8 forms the impurity diffused layer of opposite conduction type with high-density in the outer circumference of the diffused resistor and has the effects that can prevent generation of the channel and can prevent the resistance, which is the output of the diffused type gauge from being unstable.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings in which:

FIG. 1 is a drawing that shows the working example 1 in the semiconductor strain gauge relating to this invention and (a) is a vertical sectional view and (b) is a plane view viewed from an arrow B-B line direction in (a).

FIG. 2 is a drawing that shows the working example 2 in the semiconductor strain gauge relating to this invention and (a) is a vertical sectional view and (b) is a plane view viewed from an arrow C-C line direction in (a).

FIG. 3 is a drawing that shows the working example 3 in the semiconductor strain gauge relating to this invention and (a) is a vertical sectional view and (b) is a plane view viewed from an arrow D-D line direction in (a).

FIG. 4 is a plane view that shows the working example 4 in the semiconductor strain gauge relating to this invention.

FIG. 5 is a plane view that shows the working example 5 in the semiconductor strain gauge relating to this invention.

FIG. 6 is a plane view that shows the working example 6 in the semiconductor strain gauge relating to this invention.

FIG. 7 is a drawing that shows structure of the diffused type gauge in the prior art and (a) is a vertical sectional view and (b) is a plane view viewed from an arrow A-A line direction in (a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The mode of working in the semiconductor strain gauge relating to this invention is explained.

The diffused resistance region of opposite conduction type or diffused resistor is formed by diffusing the impurity on upper plane or surface of the semiconductor substrate of a fixed conduction type. The high-density impurity diffused layer of the identical conduction type to the semiconductor substrate is formed around the diffused resistor in order to prevent generation of the channel. The upper plane or surface of the semiconductor substrate is covered with a guard film, and the guard film in upper planes of a part of the diffused resistance region and a part of the high-density impurity diffused layer, that is, the guard film in a part to be connected to the electrode is removed by etching.

And, the electrode is formed with electric conductor such as aluminum and the like to enable the connection to the external circuit.

For example, as the leak is generated when the potential in type N silicone substrate becomes lower than that in type P diffused resistor or diffused resistance region, the high-density type N impurity diffused layer and type P diffused resistance region or diffused resistor are connected in positive (+) side electrode to maintain the same potential. And it is desirable to establish the high-density diffused layer of the identical conduction type to the diffused resistor under the electrode to obtain ohmic contact between the diffused resistor and the electrode.

Next, the specific working example on the semiconductor strain gauge relating to this invention is explained based on FIG. 1 through FIG. 6.

First, the working example 1 of this invention is explained referring to the drawing. FIG. 1, which shows the basic structure, shows the working example 1 of this invention that is applied to a single element. The (a) is a vertical sectional view and the (b) is a plane view viewed from an arrow B-B line direction in (a). The impurity is diffused on the surface of the type N single crystal silicone substrate 6 as a semiconductor substrate and the type P diffused resistance region (diffused resistor) 7 of opposite conduction type is formed. The guard film 8 is formed by oxide film, etc. such as SiO₂ on the surface of the type P diffused resistance region 7 and a part of the guard film 8 is removed by etching and the electrodes 9 a, 9 b are formed by metallic film such as aluminum and the like on that place. This invention is characterized in the point that a high-density type N impurity diffused layer 10 is formed so that it may surround the circumference of the type P diffused resistance region 7. Also, the electrode 9 a in positive (+) side is connected to the high-density type N impurity diffused layer 10 in the working example 1.

Next, the working example 2 of this invention is explained. FIG. 2 is the semiconductor stain gauge equipped with almost the same structure as in the working example 1 of this invention shown in FIG. 1. The (a) is a vertical sectional view and the (b) is a plane view viewed from an arrow C-C line direction in (a). The different point with the working example 1 is in the point that it adopts the structure in which the high-density type P impurity diffused layer 11 is formed on under plane of the electrodes 9 a, 9 b shown in the working example 1 and the electrodes 9 a, 9 b are connected with the type P diffused resistance region 7 in ohmic.

The other constituents are the same as those in the working example 1 described above and the identical number and identical code are given and the explanation is omitted. Next, the working example 3 of this invention is explained. FIG. 3 shows the working example 3 of this invention applied to a single element. The (a) is a vertical sectional view and the (b) is a plane view viewed from an arrow D-D line direction in (a).

The impurity is diffused on the surface of the type P single crystal silicone substrate 12 as a semiconductor substrate and the type N diffused resistance region (type N diffused resistor) 13 of opposite conduction type is formed. The guard film 8 is formed by oxide film, etc. such as SiO₂ on the surface of the type N diffused resistance region 13 and a part of the guard film 8 is etched and the electrodes 9 a, 9 b are formed by metallic film such as aluminum and the like. The high-density type N impurity diffused layer 14 is formed on the under plane of the electrodes 9 a, 9 b. This invention is characterized in the point that a high-density type P impurity diffused layer 15 is formed so that it may surround the circumference of the type N diffused resistance region 13. The electrode 9 b in negative (−) side is connected to the high-density type impurity diffused layer 15 in this working example 3.

FIG. 4 through FIG. 6 are plane views that show other working examples of this invention, that is to say, working example 4 through working example 6. Also, each plane view shows upper plane of the semiconductor substrate under the guard film. The plane shape and position of the electrode that is above the semiconductor substrate are shown with one-dot chain line for the sake of convenience.

FIG. 4 shows a half bridge structure of the type P diffused resistance region 16 and the type P resistor is used and the positive (+) side electrode 9 a and the high-density type N impurity diffused layer 17 are connected. When the type N resistor is used in the diffused resistance region, the negative (−) side electrode 9 b and the type P high-density impurity diffused layer (not illustrated) may be connected. Also, it is workable even if the intermediate electrode 9 c positioned in the middle is made to be positive (+) electrode 9 a, which is connected to the high-density type N impurity diffused layer 17.

FIG. 5 shows the semiconductor substrate of the same conduction type as the one shown in FIG. 4, however, it is the working example in which the shape of the high-density type N impurity diffused layer is different. It is the one that is formed by bending the high-density type N impurity diffuse layer 18 to fit to the shape of the type P diffused resistance region 16.

FIG. 6 shows a full bridge structure of the type P diffused resistance region 19, and the thigh-density type N impurity diffused layers 20 a, 20 b are formed outside and inside of the type P diffused resistance region 19, respectively, and the high-density type N impurity diffused layers 20 a, 20 b, which are formed outside and inside, respectively are connected to positive (+) side electrode 9 a.

Also, the other constituents in working examples shown in FIG. 4 through FIG. 6 are identical to the working example 1, which was described above, and the explanation is omitted.

Next, manufacturing method of the semiconductor strain gauge relating to this invention is explained to clarity this invention.

The process for manufacturing method of the semiconductor strain gauge relating to this invention is as follows.

(1) The impurity diffused layers that can be type P or type N diffused resistance regions 7, 13 of opposite conduction type are formed on the surface of the fixed conduction type semiconductor substrate, that is, type N or type P single crystal silicone substrates 6, 12.

(2) The high-density type N or type P impurity diffused layers 10, 15 that are identical conduction types to one of the semiconductor substrates are formed around the type P or type N diffused resistance regions 7, 13. This high-density type N or type P impurity diffused layers 10, 15 may be formed with the interval of about 5 μm with the type P or type N diffused resistance regions 7, 13. If the interval between the high-density type N or type P impurity diffused layers 10, 15 and the type P or type N diffused resistance regions 7, 13 is widened, the effect for stabilizing resistance of output of the semiconductor strain gauge is lost, and so the interval may be set within the scope of about 3 mm or less.

(3) The guard film 8 is formed on the surface of the semiconductor substrate.

(4) The guard film 8 on a part of two positions in the type P or type N diffused resistance regions 7, 13 and on an upper plane of a part of the high-density type N or type P impurity diffused layers 10, 15 are removed.

(5) Two electrodes 9 a, 9 b in which one side is connected to one position of type P or type N diffused resistance regions 7, 13 in which the guard film 8 is removed, and the other side is connected to the other position of the high-density type N or type P impurity diffused layers 10, 15 and type P or type N diffused resistance regions 7, 13 in which the guard film 8 is removed are formed.

Next, the trial cases are explained. The type P resistor was installed on the type N semiconductor substrate so that the resistance might be 3.5 kΩ by diffusion. The high-density type N impurity diffused layer was formed under the positive (+) side electrode and the high-density type N impurity diffused layer was formed under the negative (−) side electrode, respectively. The insulated guard film of SiO₂ was formed in 1 μm on the surface of the type N semiconductor substrate and the aluminum electrode with 1 μm thick was formed after a window was formed in etching. The back of the type N semiconductor substrate was ground to finish to be 25 μm thick and the dicing was carried out to obtain an element.

The size of a resistor for trial product was made to be 60 μm² in a cross section (30 μm wide, 2 μm deep), 750 μm long when the specific resistance was made to be 0.03 Ω·cm. The size of the element was able to be made to be 0.36 mm×2.73 mm×0.025 mm. The gauge rate G of the trial product was G=(ΔR/R)·(1/ε) (where ε: strain, ΔR/R: resistance variation rate), which was about 100. 

1. A method of manufacturing a semiconductor strain gauge, comprising forming a diffused resistance region of opposite conduction type to the semiconductor substrate on a surface of a semiconductor substrate of a fixed conduction type, forming around the diffused resistance region a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate, forming a guard film on the surface of the semiconductor substrate, removing parts of the guard film in a at both end parts of the diffused resistance region and on an upper plane of a part of the high-density impurity diffused layer, and forming two electrode films respectively on the both end parts of which one film is connected to one place of the diffused resistance region and the other film is connected to the high-density impurity diffused layer and the diffused resistance region such that voltage applied to the other electrode film is applied to the high-density impurity diffused layer such as to prevent current leakage from the diffused resistance region to the semiconductor substrate.
 2. A method of manufacturing a semiconductor strain gauge, comprising forming a diffused resistance region of opposite conduction type to the semiconductor substrate on a surface of a semiconductor substrate of fixed conduction type, forming a half bridge structure on the surface of the semiconductor substrate, forming around the diffused resistance region a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate, forming a guard film on the surface of the semiconductor substrate, removing parts of the guard film at three places of the diffused resistance region including both ends thereof and on an upper plane of a part of the high-density impurity diffused layer, and forming three electrode films of which any one film is connected to both the high-density impurity diffused layer and the diffused resistance region such that voltage applied to the any one electrode film is applied to the high-density impurity diffused layer such as to prevent current leakage from the diffused resistance region to the semiconductor substrate.
 3. A method of manufacturing a semiconductor strain gauge, comprising forming a diffused resistance region of opposite conduction type to the semiconductor substrate in a form of a full bridge structure on the surface of the semiconductor substrate, forming around the diffused resistance region a high-density impurity diffused layer of an identical conduction type to the semiconductor substrate on which the impurity is doped higher in density than the semiconductor substrate, forming a guard film on the surface of the semiconductor substrate, removing parts of the guard film at four places of the diffused resistance region and on an upper plane of a part of two places of the high-density impurity diffused layer, and forming four electrode films on the diffused resistance region at the four places of which any one film of the four electrode films is connected to the high-density impurity diffused layer such that the diffused resistance region and the high-density impurity diffused layer such that voltage applied to the any one electrode film is applied to the high-density impurity diffused layer such as to prevent current leakage from the diffused resistance region to the semiconductor substrate. 